Trick JavaScript Interview questions

We were asked some tricky JavaScript questions that Alex(the lead) used in interviews for the internship position. Here are some of them:

Question 1:

//What is i?
var i=0;
var add = function(){
 ++i;
    return function(){
        i++;
        return function(){
            i++;
            add();
        }
    }
};
add()()();

Question 2:

//What is the value and data type of result?
var result = !!String("false");

Question 3:

//What is result?
var result = "1"+2+4;

Question 4:

//What is 'result' and why?
var result = (function foo(bar){
 return !bar;
}(false)? false: true);

Answers:
1) 4
2) true, boolean
3) 124
4) false